Mercurial > dropbear
view libtomcrypt/src/encauth/gcm/gcm_process.c @ 1294:56aba7dedbea
options for disabling "normal" DH
author | Matt Johnston <matt@ucc.asn.au> |
---|---|
date | Mon, 02 May 2016 23:48:16 +0200 |
parents | 0cbe8f6dbf9e |
children | f849a5ca2efc |
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/* LibTomCrypt, modular cryptographic library -- Tom St Denis * * LibTomCrypt is a library that provides various cryptographic * algorithms in a highly modular and flexible manner. * * The library is free for all purposes without any express * guarantee it works. * * Tom St Denis, [email protected], http://libtomcrypt.com */ /** @file gcm_process.c GCM implementation, process message data, by Tom St Denis */ #include "tomcrypt.h" #ifdef GCM_MODE /** Process plaintext/ciphertext through GCM @param gcm The GCM state @param pt The plaintext @param ptlen The plaintext length (ciphertext length is the same) @param ct The ciphertext @param direction Encrypt or Decrypt mode (GCM_ENCRYPT or GCM_DECRYPT) @return CRYPT_OK on success */ int gcm_process(gcm_state *gcm, unsigned char *pt, unsigned long ptlen, unsigned char *ct, int direction) { unsigned long x; int y, err; unsigned char b; LTC_ARGCHK(gcm != NULL); if (ptlen > 0) { LTC_ARGCHK(pt != NULL); LTC_ARGCHK(ct != NULL); } if (gcm->buflen > 16 || gcm->buflen < 0) { return CRYPT_INVALID_ARG; } if ((err = cipher_is_valid(gcm->cipher)) != CRYPT_OK) { return err; } /* in AAD mode? */ if (gcm->mode == GCM_MODE_AAD) { /* let's process the AAD */ if (gcm->buflen) { gcm->totlen += gcm->buflen * CONST64(8); gcm_mult_h(gcm, gcm->X); } /* increment counter */ for (y = 15; y >= 12; y--) { if (++gcm->Y[y] & 255) { break; } } /* encrypt the counter */ if ((err = cipher_descriptor[gcm->cipher].ecb_encrypt(gcm->Y, gcm->buf, &gcm->K)) != CRYPT_OK) { return err; } gcm->buflen = 0; gcm->mode = GCM_MODE_TEXT; } if (gcm->mode != GCM_MODE_TEXT) { return CRYPT_INVALID_ARG; } x = 0; #ifdef LTC_FAST if (gcm->buflen == 0) { if (direction == GCM_ENCRYPT) { for (x = 0; x < (ptlen & ~15); x += 16) { /* ctr encrypt */ for (y = 0; y < 16; y += sizeof(LTC_FAST_TYPE)) { *((LTC_FAST_TYPE*)(&ct[x + y])) = *((LTC_FAST_TYPE*)(&pt[x+y])) ^ *((LTC_FAST_TYPE*)(&gcm->buf[y])); *((LTC_FAST_TYPE*)(&gcm->X[y])) ^= *((LTC_FAST_TYPE*)(&ct[x+y])); } /* GMAC it */ gcm->pttotlen += 128; gcm_mult_h(gcm, gcm->X); /* increment counter */ for (y = 15; y >= 12; y--) { if (++gcm->Y[y] & 255) { break; } } if ((err = cipher_descriptor[gcm->cipher].ecb_encrypt(gcm->Y, gcm->buf, &gcm->K)) != CRYPT_OK) { return err; } } } else { for (x = 0; x < (ptlen & ~15); x += 16) { /* ctr encrypt */ for (y = 0; y < 16; y += sizeof(LTC_FAST_TYPE)) { *((LTC_FAST_TYPE*)(&gcm->X[y])) ^= *((LTC_FAST_TYPE*)(&ct[x+y])); *((LTC_FAST_TYPE*)(&pt[x + y])) = *((LTC_FAST_TYPE*)(&ct[x+y])) ^ *((LTC_FAST_TYPE*)(&gcm->buf[y])); } /* GMAC it */ gcm->pttotlen += 128; gcm_mult_h(gcm, gcm->X); /* increment counter */ for (y = 15; y >= 12; y--) { if (++gcm->Y[y] & 255) { break; } } if ((err = cipher_descriptor[gcm->cipher].ecb_encrypt(gcm->Y, gcm->buf, &gcm->K)) != CRYPT_OK) { return err; } } } } #endif /* process text */ for (; x < ptlen; x++) { if (gcm->buflen == 16) { gcm->pttotlen += 128; gcm_mult_h(gcm, gcm->X); /* increment counter */ for (y = 15; y >= 12; y--) { if (++gcm->Y[y] & 255) { break; } } if ((err = cipher_descriptor[gcm->cipher].ecb_encrypt(gcm->Y, gcm->buf, &gcm->K)) != CRYPT_OK) { return err; } gcm->buflen = 0; } if (direction == GCM_ENCRYPT) { b = ct[x] = pt[x] ^ gcm->buf[gcm->buflen]; } else { b = ct[x]; pt[x] = ct[x] ^ gcm->buf[gcm->buflen]; } gcm->X[gcm->buflen++] ^= b; } return CRYPT_OK; } #endif /* $Source: /cvs/libtom/libtomcrypt/src/encauth/gcm/gcm_process.c,v $ */ /* $Revision: 1.14 $ */ /* $Date: 2006/11/19 19:33:36 $ */